In various industries, basic objects are sold in batches satisfying various constraints. For example, many food objects, such as fresh or frozen fish portions, chicken portions or meat portions, are sold in prepackaged batches having a predetermined weight and/or number of pieces, within given tolerance. The tolerances may be quite strict in some industries.
In the contracts between sellers and purchasers for delivery of products must satisfy minimum weight or other requirements. It is important that none of the collections is below minimum weight, but exceeding the weight results in an economical loss for the manufacturer.
The typical way to build up portions of objects is to weight each object prior to selecting the appropriate portion that is building up this particular object, where the weight of each portion is simply the sum of each individual object In that portion. If all the portions are far from the final weight limit, it is not essential which of these portions will be chosen for this object. If however the weight of one or more portions is closed to the final weight limit, it is essential which portion, for this particular object, will be chosen.
GB A 2.115.630 describes system for portion weighing of material wherein an automatic feedback correction is Introduced to correct the weighing difference between continues weighing and stationary weighing. U.S. A 3,945,448 describe similar system. As discussed hereinafter there is the fundamental difference between those prior systems, which do not allow selection of objects to be directed into preferred bin according to its first weight as well as corrected weighing for prior items already directed to a plurality of bins.
The problem with prior art methods is the inaccuracy in the weight of each portion that is building up, which can change the precondition when selecting an appropriate objects into a portion, so that the overweight of that portion is minimized. Where the weight of one portion is based on the sum of each object in the portion, the error in the weight of the total portion is the sum of errors in of each individual object. This can be related to the resolution in the weighing means that are being used. As an example the resolution in a weighing means is 1 g. This means that the error in weighing a single object is up to 1 g. If the number of objects in one portion is 20, the maximum error is number of objects multiplied with the resolution (error) for one single object, or 20*2 g=40 g. However, by registering the weight of the total portion by a single weighing procedure this error is dramatically reduced, and would in this particular example be 1 *1 g=1 g.